WO 2007/129897 discloses an apparatus for determining the flow rates and fractions of a fluid comprising a multiphase fluid in a pipe. The apparatus comprises a coaxial conductor with an inner conductor, screen and dielectric insulator mounted open ended flush with the pipe wall (cf. FIG. 13). By transmitting a signal on the coaxial conductor and analysing the reflected signal on the coaxial line due to the impedance difference between the coaxial cable and the pipe containing the multiphase fluid, the fractions of the multiphase mixture can be determined. This device is particularly suited for performing dielectric measurement of liquid films along the pipe wall at wet gas flow conditions.
WO 2007/129208 A2 discloses a microwave resonator exhibiting an impedance having a value which depends on a product to be examined by the resonator.
U.S. Pat. No. 3,213,439 A discloses a level indicating device comprising an outer cylindrical conductor 37, an inner conductor 38 and plastic or other insulating material 43 sealing the space between the conductors 37 and 38.
DE 19500559 A1 discloses a resonator comprising an outer conductor 1 and an inner conductor 2 which, at a first end of the resonator, are connected to coaxial plates of a stray field condenser 3, which plates are separated by a gap allowing a stray field to extend outside of the resonator.
US 2009/0204346 A1 discloses a system for measuring properties of a multiphase mixture flowing in a pipe. The system comprises open-ended coaxial probes which are flush mounted at the pipe wall.
WO 93/00591 A1 discloses an apparatus for measuring the complex permittivity and conductivity of a dielectric material. The apparatus comprises a structure which can be made to resonate at a radio or microwave frequency when in contact with or adjacent the dielectric material.
A problem with prior art systems and methods of the above-discussed type, however, is that they require extensive calibration.
One object of the present invention is to alleviate this problem and provide a system and a method which facilitate calibration.
Another problem with prior art systems is that they are susceptible to temperature and erosion induced measurement errors. Therefore, another object of the present invention is to provide a system and a method which can compensate for such errors.
Yet a further object of the invention is to provide a system comprising a robust and reliable measurement probe.